Obtaining the promoter sequence for a gene when only the cDNA sequence is available can be an arduous task, especially because genomic DNA libraries usually in λ phage vectors need to be screened. An easier method to obtain promoter sequence without the need for libraries is to use the technique of inverse polymerase chain reaction (IPCR) (1 ,2 ). IPCR leads to the amplification of previously unknown sequences because the primers that initially face away from each other on the linear template can be made to face each other as in normal PCR following circularization of the template (Fig. 1 ). Further amplification with nested primers ensures the integrity of the final product, which can be sequenced directly.